Marine life returning to Green Harbor River

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Humans have controlled the flow of Marshfield’s Green Harbor River for centuries. In the 1800s, at the behest of farmers who wanted more grazing land, a dike was built to limit how much tidal water flowed upstream into the river.

It was the beginning of a slow loss of habitat as the river’s salt and oxygen dropped. But recently, plant and animal species that sharply declined or disappeared are returning. From tiny invertebrates to clams and fish, the marine life is coming back.

Worms that live in the sediment have been observed on the upstream side of the dike in the last two years. Environmental officials have found six species of worm and five species of amphipod, a diminutive crustacean.

The fish are coming back, too. Species found in the river in the last two years include Atlantic silverside, banded and striped killifish, flounder, northern pipefish, sculpin, and tautog. Officials have also recorded soft shell clams, various species of crab and shrimp, snails, sea grapes, and barnacles, as well as plants that thrive in salt marshes.